Resistance Measurement - WAGO 750-489 Manual

WAGO-I/O-SYSTEM 750
750-489 4AI RTD/TC/Strain Gauge Ex i
4.7

Resistance Measurement

Standard Format
In resistance measurements, the I/O module outputs the measured values as a
process value normalized to 25000.
In the measuring range 0 ... 250 Ohm, for example, a measured value of 250 Ω
corresponds to a process value of +25000.
The resistance values are represented at a resolution that depends on the
measuring range:
• 1 digit per 0.01 Ohm (0...250 Ohm),
• 1 digit per 0.02 Ohm (0...500 Ohm),
• 1 digit per 0.04 Ohm (0...1 kOhm),
• 1 digit per 0.08 Ohm (0...2 kOhm) and
• 1 digit per 0.16 Ohm (0...4 kOhm & PTC)
in one word (16 bits).
S5-FB250 Format
For resistance measurements with S5-FB250 format enabled, the I/O module
outputs the measured values for the sensors normalized to 2500.
In the measuring range 0 ... 250 Ohm, for example, a measured value of 250 Ω
corresponds to a normalized process value of +2500.
Note: Be aware that the status information is represented in bit 0 to bit 2 and the
digitized measured value in bit 3 to bit 15. Therefore, the normalized measured
value is shifted by three bits in the process image!
Thus a normalized measured value of +2500 corresponds to a process value of
+20000.
The resistance values are represented at a resolution that depends on the
measuring range:
• 1 digit per 0.1 Ohm (0...250 Ohm),
• 1 digit per 0.2 Ohm (0...500 Ohm),
• 1 digit per 0.4 Ohm (0...1 kOhm),
• 1 digit per 0.8 Ohm (0...2 kOhm) and
• 1 digit per 1.6 Ohm (0...4 kOhm & PTC)
in one word (16 bits).
Representation in the tables: Corresponding monitoring must be switched
on!
The "Underflow", "Overflow" and "Overrange" areas require that the
corresponding monitoring is switched on (see Section "Diagnostics" > "Behavior
of the I/O Module in the Event of Error").
Process Image
Version 1.1.0, valid from FW Version 02
85
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